It can get lonely at the top, and Tony Stark is no exception. Surrounded by eye-poppingly cool gadgetry and bathing in money and fame, the captain of industry and part-time superhero has every material thing a guy could want. But as he finally comes out of the crime-fighting closet as the brains behind a special killing suit, Tony’s harboring a deep fear of mortality and suffering from a depressing mix of severe megalomania, serious daddy issues and an unrequited crush on Pepper Potts (Gwyneth Paltrow), his longtime assistant.

Needless to say, Iron Man 2 opens with a lot of troubles for the titular tough guy, which seem to seep into the fundamentals of a movie that’s mostly propped up by a few great performances and spot-on wit. Robert Downey Jr. is back as the peripatetic Tony/Iron Man, who’s beginning to unravel in the face of his own fragility. Picking up from the first installment, Tony is enjoying his celebrity and milking it for all it’s worth. One minute he’s smarming it up as emcee at his late father’s expo center, which is dedicated to all things Stark (not including the sexy dancers in spangly bikinis). The next, he’s dashing off to the nation’s capital where he charms the crowd at a senate hearing over his right to possess his hero outfit. Considering that the Iron Man apparatus can take out a small village, it’s now contested property and becomes the cornerstone of public debate over the hero’s public usefulness. Add identity crisis to Tony’s growing list of woes.

Just as he’s defending his proprietary rights, new enemy Ivan Vanko/Whiplash (Mickey Rourke) is prepping for mayhem on his gritty home turf in the former Soviet bloc. If this force of evil seems a little less than threatening — he sports stringy hair with a bad color job and grills that would make Lil’ Wayne blush — his crazy-smart engineering skills and electric coil weapons quickly reveal that he means business. Bad-hair Ivan’s past, it turns out, is intertwined with that of Tony, and the proverbial s–t is about to hit the fan. Making matters worse, sleazy Justin Hammer (Sam Rockwell) soon takes the genius Russian under his wealthy wing, setting up the perfect storm of vengeance, money, greed and really scary wires of death.

While Whiplash and Iron Man have a pre-battle that’s pretty cool on a doom-and-destruction level, the ultimate face-off never pans out the way all the build-up promises. Burning with potential and mixing whip-smart humor with a portrait of vulnerability, Iron Man 2 possesses all the elements of greatness, but never quite achieves it. Downey’s hyperactive wisecracking and increasing desperation are the fuel behind the story’s fire, which cools considerably somewhere between Vanko’s first meeting with Hammer and Tony’s unfortunate birthday party. The party scene begins as simply awkward and poignant, as the birthday boy’s interior dissolution suddenly hits fever pitch in a very public way (hint: art imitates life as booze and ego mix). Once Rhodey (Don Cheadle) gets into the act, though, things dissolve into a testosterone-charged slug-a-thon that, disappointingly, calls to mind the inanity of Transformers 2, and suddenly shifts the story from adult in-joke to adolescent pander-fest.

It’s not just Tony who’s shortchanged by some of this self-indulgence, but Pepper, too. Paltrow is her usual stunning self and manages to infuse her character with quiet confidence in Tony’s long shadow. Her role doesn’t give her much breathing room, but Pepper at least seems like she thinks for herself, even if she eventually defers to the man.

As Iron Man 2 unleashes explosions, evil plans and a lot of ass-kicking (thanks mostly to Scarlett Johansson, who plays Natalie Rushman/Black Widow) the plot plods along and then dissipates, leaving a trail of bodies and laughs but not much else. Its irrepressible humor, however, and undeniable chemistry among cast members makes the long meander fun, minus a few major digressions. Tony may have his demons to face and his humanity to confront, but for rich-guy superheroes, solving an identity crisis can be as simple as putting on a suit and saving the day.